diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 8a7999f..0e671c8 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -1761,8 +1761,9 @@
 {
 #ifdef FEAT_WINDOWS
     win_T	*win;
+    tabpage_T	*tp;
 
-    for (win = firstwin; win != NULL; win = win->w_next)
+    FOR_ALL_TAB_WINDOWS(tp, win)
 	if (win->w_alist == curwin->w_alist)
 	    check_arg_idx(win);
 #else